Oh Yay, another useless measurement of a programmer's abilities, very much as useless as the puzzle interview made popular by Microsoft and then Google. So you can measure somebody in an artificial sprint environment that has nothing to do with actually delivering a product. The real measurement is how somebody does delivering actual products to market.
it really boils down to work flow---are you actually producing output or spinning your wheels on unproductive thoughts and actions (reading hacker news, Facebook, talking on the phone). To get better, you have to maintain a consistent strong focus on producing.